1. Field of the Invention
This invention is related to axial flow pumps.
More particularly, this invention is related to axial flow waterjet pumps that discharge a solid jet of water to affect waterjet steering and reversing.
2. Description of the Prior Art
State-of-the-art waterjet pumps normally require a small diameter, solid jet of water at the pump discharge to affect steering and reversing capability and to minimize the jet diameter to avoid the boat structure. For example, axial flow pumps accelerate water through inducer/stator combinations that discharge through a necked-down housing. The complexity of the three-dimensional flows entering and passing through the stator/nozzle combination is enormous, and exact calculations of the three-dimensional velocity field to completely eliminate the resultant whirl over a range of operating conditions is beyond the current state-of-the-art. Even if the residual whirl at the stator discharge is minimal, this velocity will significantly increase as the flow is forced to smaller radii at the nozzle discharge. Whirl velocity upstream of the pump discharge nozzle destroys thrust efficiency, stability and maximum thrust of a waterjet pump. Heretofore, empirical approaches at defining the whirl problem have also been inadequate due to the complexity of the flow field and the severe environment imposed on the instrumentation.
While numerous waterjet pump patents of the type just described are in existence, none of these concepts recognize or solve the problem of tangential whirl pump efficiency losses.
Accordingly, the present invention substantially eliminates the tangential whirl that results from the fluid stream exiting the stator vanes in the housing, down the diverging pintle center body and out the discharge nozzle.